> I think the UK is more like 10C and a global average is roughly half
> that. This would suggest that on the global scale the effect would be
> very much at (below) the bottom end of your range. Of course I agree
> that on a local basis the elimination of all aerosols could have rather
> larger effects.
I've looked up the monthly averages for Birmingham and Ekaterinburg
and the difference between January and July is 13C and 34C
respectively.
I don't know the hemispheric averages for seasonal changes or the
forcing changes for the whole hemisphere, which I suspect would be
smaller than 200 W/m2.
The beauty of using the whole hemisphere is that relatively little
heat crosses the equator, while a lot of heat makes its way from the
tropics to England (?).
The beauty of looking at individual locations is that it gives an idea
of how important the difference between continental and ocean
locations is, and I suppose faced with a step change in aerosol
forcings, there'd be a much more pronounced difference in warming
rates between ocean/land than is the case now.
> I don't think there is any suggestion that aerosols globally have
> actually declined significantly (the emissions rate per power output may
> have improved, but total power has increased). Crowley's forcing data
> has aerosols monotonically increasing to 1998.
Michael Tobis presented a link to a presentation and summarised it as
showing a recent decline in Chinese aerosol forcing. Without having
read the presentation, I thought that might be due to lower sulphur
coal or recent pollution abatement efforts. After reading the
presentation, I think it was only based on the well known dip in
Chinese coal use at the end of the 1990's recorded by official Chinese
statistics, which was followed by a near unbelievable doubling within
five years.
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